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Friday, February 26, 2010

Researchers in Budapest recently formulated an explanation for why horses might want to be white (from an evolutionary perspective). White horses are more susceptible to skin cancer (of all things) and predation. Well, they do stand out, so higher predation risk isn't too surprising.

But, it turns out the white coats reflect less polarized light than dark horses, which actually makes them less visible to horseflies. Hiding from one risk, while exposing themselves to others.

This story caught my eye, because it highlighted a few aspects of diversity ecologists have been mulling over for a while now. Different traits within a population often trade off between adaptation to one selective pressure (predation, drought, resource depletion, etc.), at the expense of greater risk from another one. These trade-offs can allow a diversity of traits to persist within a population, so long as each experience positive fitness on average.

This is similar to the arguments proposed in the insurance hypothesis by Michel Loreau and Shigeo Yachi, but applied to individuals within a species, rather than species within a community. But the net effect is the same: stabilization and reduced extinction risk at higher aggregate levels of organization. Individual-scale variation may also play an important role in species coexistence at the community level.

Do trade-offs drive evolutionary and ecological dynamics? Do they promote diversity at all scales?

In other news, danish & japanese researchers found yet more evidence that Biology is freaky. They were able to show that changing the concentration of oxygen in water above sediments devoid of macrofauna, directly led to changes in hydrogen sulfide concentrations more than 12 mm below the oxic zone, mediated entirely by electron transfer between bacteria through the sediment to the surface (interface with the overlying water column).

In other words, the bacteria in the sediment created an electric current to drive cellular metabolism and use molecules millimeters away as electron acceptors! That's like running while being powered by a battery sitting a mile away in your house!